Rope stretch compensator for suspended conveyances in mine hoisting equipment



Nov. 24, 1964 D. M. BENTLEY 3,158,228

ROPE STRETCH COMPENSATQR FOR SUSPENDED CONVEYANCES IN MINE HOISTING EQUIPMENT Filed July 16, 1962 3 Sheets-Sheet 1 INVENTQR DES MOND M. BEN-hay ATTORNEY Nov. 24, 1964 D M. BENTLEY 3,158,228

ROPE STRETCH COMPENSATOR FOR SUSPENDED CONVEYANCES IN MINE HOISTING EQUIPMENT Filed July 16, 1962 3 Sheets-Sheet 2 INVENTOR Des MOND M. BENTLEY ATTo RNEY Nov. 24, 1964 D. M. BENTLEY RGPE STRETCH CDMFENSATOR FOR SUSPENDED CONVEYANCES IN MINE HDISTING EQUIPMENT 5 Sheets-Sheet 5 Filed July 16, 1962 I INVENTOR Dzsmmo M. BENTLEY ATTORNEY United States Patent ROPE STRETtIH COMPENSATOR FOR SUPENDED CONVEYANCES IN MlNE HGISTING EQUIP- MENT Desmond M. Bentley, Johannesburg, Transvaal, Republic of South Africa, assignor to Anglo American Corporation of South Africa Limited, Johannesburg, Transvaal, Republic of South Africa Filed July 16, 1962, Ser. No. 214L111 Claims priority, application Republic of South Africa July 18, 1961 14 Claims. (Cl. 1187-32) This invention relates to mine hoisting systems in which 'a conveyance, suspended from a lengthy rope, is required to be stopped at diiferent stations during its upward and downward movement for loading and unloading to take place.

The eifective length of the supporting rope is dependent upon the length of the unwound rope and upon the loading of the conveyance. Where the rope is long, its stretch can be considerable and indeed where ropes of the order of 7500 feet or more are in use the stretch, towards the bottom of the path of the conveyance, may be of the order of seven feet and more. It must also be pointed out that, as the conveyance is loaded or unloaded, so does the stretch increase or diminish.

The desirability of locating the conveyance at the corroot level of a station, and to keep it there despite change in loading is self-evident. In current practice, the hoist driver is required to use his judgment and reliance on him is not always justified.

The object of the present invention is to provide a hoisting system in which corrections are automatically made for rope stretch resulting from the weight of the suspended rope itself and from varying loads, so that the conveyance arrives at each station at the correct decking level and remains there as loading or unloading proceeds, without the exercise of judgment on the part of the driver.

According to the invention, the system comprises mine hoisting equipment including a shaft, a hoist, a cage within the shaft, a hoist drum, a rope between the drum and the cage, a head sheave above the shaft over which the rope passes, means to vary the height of the head sheave and means so to govern the height-varying means as to hold the cage at a predetermined level.

Further according to the invention, the height of the sheave is varied, in accordance with the load on the conveyance. To this end, the structure supporting the sheave includes a device continuously to evaluate the load on the conveyance, and to apply such evaluation to the sheave height-varying means.

In another aspect of the invention, the height of the sheave is varied by a device that scans the position of the conveyance and actuates the height-varying means to level the conveyance.

Also according to the invention, and common to both aspects, is a hydraulic system including a hydraulic ram supporting the sheave and means to energize the ram to lift or lower the sheave, in accordance with information fed to it by the load-evaluating or the scanning device.

Preferably, the sheave depends from the plunger of the ram, the cylinder being fixed, but the converse can apply. The hydraulic system is preferably a constant pressure system and the admission to and withdrawal from the cylinder of hydraulic fluid are controlled by valves which are themselves controlled by the load-evaluating or the scanning device.

Several embodiments of the invention are schematically illustrated in the accompanying drawings in which FIGURE 1 is a view of the first embodiment,

FIGURE 2 is a view of the second embodiment,

Patented Nov. 24., 1964 FIGURE 3 is a view of part of the hydraulic system common to both the first and second-embodiments and FIGURE 4 is a view of a third embodiment.

In both embodiments, the cage 10 is supported on a rope 12 that passes from a winding drum 14 over a head sheave 16, and down the shaft 18 to the cage.

The level in the shaft at which the cage is to be loaded or unloaded is shown at El). There may, of course, be several such levels.

The head sheave 16 hangs from the plunger 22 of a hydraulic ram of which the cylinder 24 is fixed on the headgear. The hydraulic system of which the ram is a part is a constant-pressure system and comprises oil pumps 25 operating intermittently to draw oil from a sump 28 and deliver it under pressure to a hydraulic accumulator 30 through non-return valves 32, stop valves 34 and pressure relief valves 35.

The supply to and discharge from the cylinder 24 is controlled by a two-way valve 36.

In the embodiment of FIGURE 1 the height of the sheave 16, or the position of the plunger 22 in the cylinder 24 that determines the height of the sheave, is varied in accordance with the total weight supported by the sheave. The total weight is, of course, the weight of the cage itself, the Weight of its load, and the weight of the rope between the sheave 16 and the cage. The weight of the cage is known and invariable; and the weight of the rope is calculable in respect of elevation of each level 20. The weight of the load is unpredictable, but for any given load at a given level the extension of the rope due to the load is exactly calculable. Thus, if the weight of the load be known, adjustments can be made to the height of the sheave to ensure that the cage is located with precision at the appropriate level. To this end, the sheave-supporting structure includes a device continuously to evaluate the load on the conveyance. This, in the drawing, is a load cell 38 included in an electrical circuit that comprises an amplifier 40 that feeds amplified signals from the load cell to a mixer unit 42; a proportioning unit 44 (which may also act as a recording unit if the loads handled by the cage are to be recorded and integrated) and a solenoid 46 to control the valve 36.

Into the mixer unit 42 are also fed signals corresponding to the tare weight of the cage, through a rheostat signal 48; and signals corresponding to the varying weight of the suspended rope. The latter signals are automatically applied through a drive 50 from the winding drum 14 that operates a rheostat 52 in accordance with the depth of the cage below the surface. The mixer unit 42 is essentially a subtraction unit as it subtracts the signals corresponding to the tare Weight of the cage and the weight of the suspended rope from the signals from the load cell i.e. the tare weight of the cage, the weight of the suspended rope and the weight of the load in the cage, to give as an output a signal corresponding to the weight of the load in thecage. This output from the mixer is fed to the proportioning unit 44.

The proportioning unit 44 has two other inputs. Firstly it is fed with a signal from rheostat 53 which corresponds to the length of the unwound rope. Secondly it is fed with a signal from rheostat 57 which is indicative of the position of the plunger 22 in the cylinder 24. In the proportioning unit 44 the output signal from the mixer (which corresponds to the weight of the load in the cage) is multiplied with the signal from the rheostat 53 (which corresponds to the length of unwound rope) and Youngs Modulus for that rope to give a signal corresponding to the amount of stretch in the rope at that time. This signal is then compared with the signal from rheostat 57 and if there is any discrepancy between the two the plunger is moved up or down according to which of the two signals is greater. 7

For example assume that the plunger is at a position two feet above the lowest point in the cylinder (the datum line) and the stretch signal (i.e. the product of the signals from the output of the mixer and the rheostat 53 and Youngs Modulus for that rope) is of such an amplitude that the plunger and thus the sheave has to be moved three feet above the datum line to ensure that the cage is held at the required level, the plunger will be moved upwards by a distance of one foot.

The plunger is controlled by the valve 36 which in turn is controlled by the solenoid 46. The solenoid is operable by the output from the proportionin g unit 44. Therefore in the above example the output signal from the proportioning unit 44 will be of such a magnitude that the valve 36 will only be opened a time long enough for the plunger to be moved upwards by a distance of one foot.

The corrected load cell signal of net load is preferably measured and electronically recorded only while the cage 10 is stationary, in order to eliminate the effects of dynamic rope stresses. During this process the equipment is continuously operative to compensate for cage load variations which occur during loading and unloading operations.

To this end the drivers brake is associated with a switch 56 that is open while the cage is in motion thus isolating the mixer unit from the proportioning unit while the cage is in motion. During motion of the cage the proportioning unit derives an output by multiplying the corrected and recorded load cell signal with the signal from the rheostat 53 and Youngs Modulus so that the plunger is still operative even though the cage may be in motion.

In the embodiment of FIGURE 2 the hydraulic system described above is also utilized. However, the control of the system is achieved diflerently from that of FIGURE 1. In this embodiment, the position of the cage itself is monitored at the desired level or levels.

The position of the cage within the shaft is signalled by any suitable scanning means such as proximity switches l 60, or scanning devices such as photo-electric cells, ultrasonic means and so on. The signals are transmitted up the shaft, by means of cables or at carrier frequencies on the hoisting rope, to the control gear in the headgear which consists in a solenoid 46 the armature of which controls the valve 36 to feed pressure oil into, or Withdraw it from, the cylinder 24. This system only operates to provide cage levelling once the driver has applied his brakes for stopping at a particular station 26. Each station must be equipped with cage position-sensing elements such as the proximity switches 60 and the cage must be brought to rest within the scanning range of these elements.

It will be seen that the devices of the invention provide for the automatic correction of the diiference in stretch of hoist suspension ropes due to variation in the attached load under loading or unloading circumstances, thereby maintaining the conveyance level with the underground station which is being served.

Where the net loading is utilized asin FIGURE 1, correction is made automatically for the variation of stretch with length of the suspended rope for any specified load, during the hoisting cycle, so that the conveyance will arrive at the correct decking level at any shaft station or elevation without any premeditated judgment on the part of the hoist driver.

In the embodiment of FIGURE 2, all the driver need do is to brake the cage within fixed marks and the cage is then automatically levelled during loading and unload- In the system shown in FIGURE 1 the entire equipment required is out of the hoisting shaft and above the shaft collar. Further, one installation will serve any number of operating stations in the shaft, without extensions to the equipment.

In both aspects of the invention, the equipment can be used on single or multiple rope winding, and in the latter case, use can be made of the equipments ability to equalize the rope tensions hydraulically.

Thus, in FIGURE 4 the shaft 13 accommodates two cages iii, 72 in balance, as in the well-known Koepe hoist. Each cage is supported by two ropes '74, '76 which pass around a friction drum 78.

Each bight of each rope 74, 76 has its head sheave 8t}, 82, 84 or 86, and each sheave is supported by the plunger of a hydraulic ram 88, 9t), 92, 94, as in the embodiments above described. The two rams appropriate to each cage are paired in the same hydraulic circuit, of which, of course, there are two, one for each cage.

Since the cylinders of each pair of rams are interconnected in the hydraulic system, differential rope stretch in respect of each pair of ropes supporting a cage is automatically compensated for, since the two plungers will take up positions in which the rope tensions are equal.

Other advantages of the devices of the invention which might hear mention are that fluid pressure failure is not serious as the system merely reverts to conventional operation; that the device of the invention, as far as it relates to load-evaluating, can be installed in a working shaft without disrupting normal shaft usage; that maintenance is simple and done at the surface and that there is no danger of damage to the equipment during unloading and loading of heavy material and supplies.

I claim:

1. Mine hoisting equipment including a shaft, a hoist, a cage within the shaft, a hoist drum, a rope between the drum and the cage, a head sheave above the shaft over which the rope passes, means to vary the height of the head sheave and means so to govern the heightvarying means as to hold the cage at a predetermined level.

2. The equipment of claim 1 in which the heightvarying means comprises a hydraulic ram the movable member of which supports the head sheave; a hydraulic system including the ram, a source of pressure fluid, and a valve to control flow of fluid into and out of the ram; and in which the governing means so operates the valve as to feed pressure into and withdraw it from the ram suitably to hold the cage at the predetermined level.

3. The equipment of claim 2 in which the hydraulic system is a constant pressure system incorporating a sump for hydraulic fluid, a pump to draw fluid from the sump, an accumulator for pressure fluid delivered by the pump, a pipe to deliver pressure fluid for the accumulator to the ram, and a pipe to lead fluid exhausted from the ram back into the sump.

4. The equipment of claim 3 in which the valve is an electro-hydraulic valve and in which the governing means includes a solenoid or motor that controls the movable member of the valve.

5. The equipment of claim 4 in which the solenoid or motor is included within an electrical circuit comprising means to generate a signal proportional to the weight of the cage and of the suspended part of the rope.

6. The equipment of claim 5 in which the signal-generating means is a means that continuously senses the Weight of the cage and of the suspended rope; and the electrical circuit includes an amplifier for the generated signal and means to correct the signal for the tare weight of the cage, for the weight of the suspended rope and for the predetermined rope stretch due to the tare weight of the cage and the weight of the suspended rope.

7. The equipment of claim 6 in which the correcting means for the weight and stretch of the rope are rheostats controlled by the hoist drum and arranged to feed correcting signals into the electrical circuits.

8. The equipment of claim 7 in which the correcting means for the tare Weight of the cage is a predetermined and prc-set signal fed into the electrical circuit.

9. The equipment of claim 8 including means to brake the drum and a switch in the electrical circuit operated by the brake to hold the circuit open while the drum is in motion and to close the circuit when the drum is braked to a standstill.

10. The equipment of claim 4 in which the solenoid is included Within an electrical circuit comprising means to sense the location of the cages within the shaft and to generate a signal in proportion to such location.

11. The equipment of claim 10 in which the sensing means is a scanning means located Within the shaft at the predetermined level.

12. The equipment of claim 11 in which the scanning means is a series of proximity switches.

13. The equipment of claim 2 in which the cage is supported on multiple ropes, each of which is supported by a head sheave having means to vary the height of the sheave and in which each head is suspended from a hydraulic ram both or all the rams being interconnected and included in a single hydraulic system.

14. The equipment of claim 2 in which there are two balanced cages in the shaft, each supported by one or more head sheaves individually variable in height; the sheave or sheaves of each cage being included in a hydraulic system.

References Cited in the file of this patent UNITED STATES PATENTS 998,629 Neenan July 25, 1911 1,126,260 Neenan et a1. Jan. 26, 1915 1,261,624 Ritter Apr. 2, 1918 1,268,110 Furlow June 4, 1918 1,861,063 Palm May 31, 1932 2,308,211 Sanford Jan. 12, 1943 FOREIGN PATENTS 1,064,703 1959 Germany Sept. 3, 

1. MINE HOISTING EQUIPMENT INCLUDING A SHAFT, A HOIST, A CAGE WITHIN THE SHAFT, A HOIST DRUM, A ROPE BETWEEN THE DRUM AND THE CAGE, A HEAD SHEAVE ABOVE THE SHAFT OVER WHICH THE ROPE PASSES, MEANS TO VARY THE HEIGHT OF THE HEAD SHEAVE AND MEANS SO TO GOVERN THE HEIGHTVARYING MEANS AS TO HOLD THE CAGE AT A PREDETERMINED LEVEL. 